Article coating apparatus



Sept 8 l959 J. A. ROEDER ErAL 2,902,971

ARTICLE coATING APPARATUS Filed Feb. l2, 1957 2 Sheets-Sheet 1 IA l A fr

ff/m@ L/A 5755555' W5 755555 Sept. 8, 1959 .1.A. RQEDER EI'AL ARTICLEcoATING APPARATUS 2 Sheets-Sheet 2 Filed Feb. 12, 1957 ra waz/zw wUnited tes Patent O ARTICLE COATING APPARATUS Joseph A. Roeder,Quakertown, and Walter J. Tesche,

Coopersburg, Pa., assignors to Western Electric Company, Incorporated,New York, N.Y., a corporation of New York Application February 12, 1957,Serial No. 639,712

2 Claims. (Cl. 118-11) This invention relates to article coatingapparatus and particularly to the application of protective coatingsover prescribed areas of articles such as asymmetrically conductivediscs or wafers of varistors.

The asymmetrically conductive element utilized in dry disc rectiers,such as the Western Electric Company type 44A copper oxide varistor, isa so-called copper oxide disc which is metallic copper with an adherentlilm or layer of copper oxide on one of its hat faces. The discs, andterminals in contact with the opposing faces thereof, are assembled inmetal housings or cans having apertures through which the terminalsprotrude. In such devices, the junction between the oxide and the metalmust be protected Ifrom exposure to the air and moisture to avoiddeterioration of its asymmetric properties. This protection has beenprovided heretofore by vacuum-impregnating the assemblages with a waxymaterial such as polyethylene-polybutene compound, the compoundpenetrating and lling the interiors of the housings through the terminalapertures therein. While effective for its intended purpose, thisprocedure has the disadvantage of requiring the use of considerablevolume of the compound and the introduction of a degreasing or othercleaning operation to remove the compound -from the terminals and theoutsides of the housings.

The object of the invention is to improve such devices and reduce thecost of making them by limiting the application of the protectivecoating to areas where they are required thereby conserving coatingmaterial and eliminating the need for a cleaning operation.

A preferred embodiment of the invention Ifor doing this utilizes amovable Vacuum holder for holding the disc by engaging the centralportion of the oxide layer on the one face which need not be, and is notcoated with the sticky compound so that the vacuum holder may ybemanipulated freely to discharge the coated discs therefrom into thehousings in the assembly of the devices. The loaded vacuum holder ispositioned in a support accurately locating one or more of the discshorizontally above a vertically movable ladle normally submerged in aheated reservoir for melting the compound and keeping it uid at auniform viscosity. An actuator automatically lifts the ladle through theheate-d compound in the reservoir, lling it to overowing when the discholder is placed in its support. The ladle is moved up only until thelower portion of the `discs including the edges thereof are submerged inthe filled ladle, the meniscus of the compound extending slightly on tothe top oxide layers to surround completely the exposed edges of therectifying junctions. The ladle is held in the raised positionsufficiently long to permit the compound to coat the discs adequatelywhen it is automatically lowered and a heated scraper member isreciprocated across the lower faces of the discs to remove surpluscompound therefrom. The disc holder is then removed from the supportmoved to an associated assembly jig where the discs are dis- 2,902,971Patented Sept. 8, 1959 ICC charged therefrom in proper assembly relationwith the terminals preassembled in the housings for the devices. These'and other features of the invention will be more fully understood fromthe following detailed description taken in conjunction with theaccompanying drawing, in which:

Fig. l is a side elevational View of an apparatus for `coating varistordiscs;

Fig. 2 is an enlarged View, with portions broken away, of the discholder support structure of the apparatus of Fig. l;

Fig. 3 is an enlarged View along the plane of line 3-3 of Fig. l,showing the scraper member in crosssection;

Fig. 4 is a perspective view of the supply and assembly jig; and

Fig. 5 is a schematic diagram of the control circuit for the tixture.

Referring now to Fig. l of the drawing, the main parts of the apparatusshown therein include a reservoir 7 for the liquid protective coatingmaterial 77, a main frame `8, a vertically movable ladle 9 normallysubmerged in the material 77, a reciprocatable scraper 12, a movablevacuum-controlled disc holder 14 and a support 15 for accuratelylocating the holder 14 so that the varistor discs 16 will be supportedin a prescribed vertical position. The reservoir 7 istemperature-controlled and heated so that the viscosity of the waxycompound therein will remain substantially uniform and free flowingduring the operation of the device. For polyethylene-polybutenecompound, the temperature of the melt is maintained at about `degreescentigrade. Heating means for such a reservoir are well known in the artand are not included in the drawing.

The ladle 9 is supported on an arm 17 connected to the movable actuatorelement 18 of a double-acting air cylinder 19 attached to a bracket 36on the frame 8. The ladle is movable vertically to a prescribed verticalposition as determined by an adjustable stop member 22 on a bracket 23on the frame 8. A fixed guide member 24 also supported from the bracket23 is slidably positioned within a hole through the ladle arm 17 inorder that the ladle 9 will traverse a prescribed vertical path wheneverthe air cylinder 19 is actuated. In its raised position discs 16 on theholder 14 will have their lower faces and the peripheral edges submergedin the lilled ladle, the meniscus of the compound extending over and onto the top oxidized faces of the discs, as seen in Fig. l. The operationof the air cylinder 19 is controlled by a solenoid control valve 25 onthe frame member 8, the operation of which will be discussed below inconnection with the description of the control circuit of Fig. 5.

The laterally extending arm 28 of the scraper 12 is heated by aresistance element 29, energized from a source not shown, in order tokeep the compound from solidifying and accumulating thereon. Arm 28 ismounted to a horizontally reciprocatable member 32 connected to theactuator of a double-acting air cylinder 33, whose operation iscontrolled by a solenoid control valve 34. When actuated, the aircylinder 33 reciprocates the scraper arm 28 along a horizontal plane, asviewed in Fig. l, so that the top edge 37 will pass across the lowerfaces of the discs 16 on the holder 14 and scrape surplus compoundtherefrom. A lixed guide element 35 on the bracket 36 keeps the member32 from twisting to maintain the scraper arm 28 horizontally disposed.

The disc holder 14 is movable between the support 15 of the waxapplicator and the jig shown in Fig. 4 which may be located in front oralongside of the coating apparatus. The holder 14 includes a hollowsteel shaft 42 having a bifurcated end piece 43, an internal passagebeing provided from the hollow shaft through the end piece to thedisc-supporting lower extensions 44. The hollow shaft 42 is connectedthrough iiexible tubing 45 to the output of a vacuum pump through acontrol valve 46 conveniently mounted alongside of the jig of Fig. 4.The valve 46 is normally open to provide suction at the extensions 44 tohold the discs 16 securely thereto. When the push button valve 46 isdepressed, the vacuum path to the extensions 44- is broken and discssupported thereon will drop off as required, for example, in theassembly of the coated discs in the housings 65. The end piece e3 of theholder is provided with a locating wedge 47 extending therefrom whichmay be slidably positioned in the V-slot of locating blocks 48 and 67 onthe jig of Fig. 4, which permits locating extensions 44 either above theV-notches in a plate 49 on the top of the jig wherein varistor discs lr6to be coated may be picked up by the holder 14 or for depositing coated`discs in assembled relation with terminals 61 in housings or cans 65`accurately positioned in holes in a base plate 66 for the jig. lnloading the discs on the holder, the operator need only slide the discsi6 into the V-slots, with the oxidizing layer side 4facing upwardly,then move the holder 14 down, sliding the locating wedge `i7 in theguide block 48. Once the holder has been loaded, it is positioned in thesupport of the coating apparatus which is shown in detail in Fig. 2.

An upper member 52 of the support ,l5 is mounted on the frame extension54 and has a vertically extending V-groove 49 for receiving they shaft42 of the disc holder, permanent magnets 53, mounted in each of theinclined faces, providing magnetic attraction `for the shaft 42. Thelower portion of the support l5 is mounted on the member 56 on the`frame extension 54. The lower end of the member 56 has a V-notch forreceiving the wedge 47 of the end piece 43 and an extension 57, mountedon the bottom of the member 56, provides an accurate vertically locatedplatform for receiving the bottom surface of the end piece 43. 62 in ablock 58 on the member 56 provides an attractive yforce to hold thelower portion of the shaft 42 thereto. This block 58 also has a Verticalbevelled surface 59 for engaging a similarly bevelled surface 60 on thetop of the wedge 47 of the end piece 43. When the holder 14 ispositioned on plate 57 with the wedge 47 nested within the V-slot at theend of member 56 and against the bevelled Surface 59 of the block 5S,discs 16 on the holder will occupy a predetermined vertical positionwith respect to the raised position of the ladle 9 and also the scrapingedge 37 of the scraper arm 28.

A microswitch 63 on the `frame extension 54 having an actuator 6ftextending through the upper locating block S2 is operated when theholder 14 is positioned in the support l5. This switch triggers theautomatic operation of the fixture which will be discussed below.

Referring now to Fig. 5, the automatic operation of the wax applicatorwill be described. The control circuit is triggered by the operation ofmicroswitch 63 when the disc holder 14` is placed in the support 15.This microswitch closes to complete the circuit from an alterhatingcurrent source 74 to a transformer 75, a timer 72, and a time delayrelay 73. When the transformer 75 is energized, the winding 76 of thesolenoid control valve is energized through the normally closed contacts82 of the timer 72 to supply compressed air from a source, not shown, tothe air cylinder i9 to immediately raise the ladle 9 through the vuidpolyethylene-polybutene compound 77, the lled ladle 9 being lifted to avertical position as controlled by the stop member 22 which makescontact with the raised actuator 18 of the air cylinder. In the raisedposition, the accurately located lower faces and the peripheral edges ofthe discs i6 are submerged in the wax-filled ladle with the meniscus ofthe compound extending Slightly over the junction edge of the copper Apermanent magnet i 78 and a relay 86 through the contacts 85 of the nowoperated time delay relay 73 which prepares the circuit for operation.The operated contacts 87 of relay 86 complete the energizing circuit ofwinding 88 in the solenoid control valve 34 which operates to supply airto the air cylinder 33 to move the scraper ll?. across the lowersurfaces of the discs i6 to wipe the surplus wax therefrom. After aboutthree seconds, the timer 78 times out, opening contacts 89 tode-energize the winding 88 and closes the contacts 90 to energize thewinding 91 of the solenoid control valve 34 to cause the air valve 33 toretract the scraper to its original position. When the holder 14 isremoved from the support 15, to drop the coated discs i6 in the jig,microswitch 63 will again open and thereby reset the timers to preparethe apparatus for its next operation. The contacts of delay relay 73,which are timed to close after the ladle 9 is raised and before it islowered, are included in the energizing circuit of timer 7 S and itsassociated solenoid control valve 34 to prevent false operation of thescraper immediately after' the triggering switch 63 is closed and beforethe ladle is raised opening switch 78.

lt is to be understood that the above described arrangements are simplyillustrative of the application of the principles of the invention.Numerous other arrangements may `be readily devised by those skilled inthe art which will embody the principles of the invention and fallwithin the spirit and scope thereof.

What is claimed is:

l. apparatus for applying viscous coatings to articles with flatsurfaces, comprising having a heated, temperature-controlled coatingmaterial reservoir lfor maintaining the viscous material in a uid state,a ladle normally submerged in the material in the reservoir, means forsupporting the articles with the fiat surfaces thereof disposed in acommon horizontal plane above the reservoir, means for lifting the ladle`t'orongh the material, means for arresting the motion of the ladle toposition the ladle above said horizontal plane to submerge onlyprescribed portions of the articles, means for automatically loweringthe ladle when the articles are coated, an elongated element having ascraping edge lying within said common plane, a heater for the elementto keep scraped coating material from adhering thereto, means forreciprocating the element to move the scraping edge in the common planepast the articles to remove excess material from the coated flatsur-faces thereof, and means responsive to the lowering of the ladle foractuating the reciprocating means after the articles are coated.

2. An apparatus for applying viscous coatings to articles with ilatsurfaces, comprising having a heated, temperature-controlled coatingmaterial reservoir for maintaining the viscous material in a fluidstate, a ladle normally submerged in the material in the reservoir, aholder for the articles for supporting the articles with the flatsurfaces thereof disposed in a common plane above the reservoir, asupport for the holder for positioning said connnon plane horizontallyat a predetermined height above the reservoir, means responsive to theplacement of the holder in the support for lifting the ladle through thematerial, means arresting the motion of the ladle to position the ladleabove said horizontal plane to submerge only prescribed portions of thearticles, means for automatically lowering the ladle when the articlesare coated, an elongated element having a scraping edge lying withinsaid horizontally disposed common plane,

5 a heater for the element to keep scraped coating material fromadhering thereto, means for reciprocating the element to move thescraping edge in the common plane past the articles to remove excessmaterial from the coated flat surfaces thereof, means responsive to thelowering of the ladle for actuating the reciprocating means after thearticles are coated, and means rendering the reciprocating meansinoperative for a predetermined time after the holder is placed in thesupport to permit coating the articles before the scraper is actuated.

References Cited in the le of this patent UNITED STATES PATENTS ShearerJuly 27, 1939 Zabel Mar. 20, 1951 Dilts Sept. 23, 1952 McLaughlin et alApr. 20, 1954 Orrell et al. Feb. 21, 1956

